From Alaska to Argentina and back: migration routes, migration timing, and wintering areas of adult male Swainson’s Thrushes ( Catharus ustulatus ) from breeding areas in interior Alaska

Adult male Swainson’s Thrushes (Catharus ustulatus) from interior Alaska complete among the longest round-trip migrations of any North American migratory passerine, traveling from their breeding grounds to wintering areas in South America and back. This study reveals that these birds exhibit a leapfrog migration pattern, wintering farther south than those from more southern latitudes, and use distinct routes during autumn and spring migrations. Using archival light-level geolocators and GPS loggers, researchers tracked 16 individuals, documenting their cross-continental migration across Canada, stopover behaviors, and wintering areas in Colombia and Argentina. Autumn migration begins by early September, with birds arriving on their wintering grounds by mid-November, while spring migration starts in late February, culminating in their return to breeding grounds by late May. The findings highlight the importance of forested landscapes across their annual range.

McIntyre, C., Stenhouse, I., Adams, E., Gilbert, A., Boelsma, J., Gress, G., Grigsby, C., Reppert, J., Phillips, L., Williams, E., & Weidensaul, S. (2026). From Alaska to Argentina and back: migration routes, migration timing, and wintering areas of adult male Swainson’s Thrushes ( Catharus ustulatus ) from breeding areas in interior Alaska. Avian Conservation and Ecology, 21(1). https://doi.org/10.5751/ace-03016-210111